Twin Falls County, ID Environmental Rules: Erosion Control (2026)

The requirement sits in section 8-21-7, the general requirements section that applies to every wind and solar energy project the county reviews, whether personal-use, small-scale, or large-scale. Subsection (B) requires applicants to regularly water or otherwise treat unpaved roads and staging areas throughout site development and construction to keep dust and wind erosion down. Subsection (C) goes further for anything that disturbs enough ground to trigger federal permitting: the applicant must do all roadwork and other site development in compliance with a National Pollutant Discharge Elimination System permit under EPA rules, and must hand the county copies of that NPDES permit and an erosion and sediment control plan when the application is submitted.

That plan has to include measures that keep local roads and adjacent land from being damaged by runoff or sediment during construction. The same drainage and erosion control plan is listed again among the application materials required under section 8-21-3(G)(7). Outside of energy projects, Twin Falls County has not written a standalone grading or sediment-control ordinance in its own words; general building work instead falls under the adopted International Building and Residential Codes referenced in Title 7, Chapter 1.